1. Field of the Invention
The present invention relates to a method and rolling equipment line for use in endless rolling, in which the trailing edge of a sheet being fed and the leading edge of another sheet subsequent thereto are joined to each other on the input side of hot rolling equipment to continuously roll the sheets, the method and rolling equipment line quickly imparting an appropriate sheet crown to each sheet independently of changes in sheet thickness, sheet width or sheet material.
2. Description of the Related Art
Endless rolling, in which the trailing edge of a sheet being fed and the leading edge of another sheet subsequent thereto are joined to each other on the input side of hot rolling equipment to continuously roll the sheets, is advantageous in that any trouble caused during sheet passage can be reduced and that a substantial expansion of rolling limit can be expected (See Japanese Laid-Open Patent Application No. 4-262804).
As disclosed in Japanese Laid-Open Patent Application No. 62-3818, in sheet crown control for a rolling system as described above, errors in sheet thickness or anticipated load errors are generally ascertained at each stand of rollers and, on the basis of the errors thus ascertained, the load of the roll bender is adjusted, thereby attaining the target sheet crown.
However, this endless rolling, described above, has the following problem:
If the sheets to be joined together are made of the same material and have the same thickness, it is possible to continue rolling without any change in the set conditions for the rolling mill. In reality, however, the material and size of products to be obtained through hot rolling varies greatly. That is, the sheets to be rolled are not always of the same material or size.
To make the most of endless rolling, sheets of different materials and sizes have to be joined to each other.
To impart a desired sheet crown to each sheet to be rolled, it is necessary to change, during the feeding of the sheets, the mechanical crown to be imparted by the upper and lower work rolls so as to keep the mechanical crown of each sheet in conformity with a target sheet crown value, in accordance with changes in rolling load and changes in the target crown for each sheet.
However, the conventional technique of changing the roll bender load for the purpose of changing the mechanical crown is disadvantageous in that the control range is very small.
Generally speaking, it is only possible for the roll bender to apply a force which is within approximately .+-.120 t of the stress limit of the roll chock, and the amount of change of the mechanical crown in this case is as small as approximately 600 .mu.m.